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Why is pastrami iridescent?

Ever wonder why corned beef, pastrami or other sliced deli meats have a sheen? Think of it as the eating rainbow.

The light bounces off the surface of the deli meat, a phenomenon known as “diffraction,” Nadia Arumugam writes in Slate. The color of the meat matters, she says. Turkey and chicken are too pale.

She explains the process:

A piece of meat is composed of strands of fibers that are tightly packed together in parallel bundles. After meat is sliced, the cut ends of the fibers form a series of grooves, like the top of a picket fence. White light is composed of a spectrum of different colors, and each one of those colors has a specific wavelength. When white light hits the grooves on the surface of a deli meat slice, some of the light is absorbed and some of it is reflected. Each component color wave of the reflected light bends at a different angle depending on its particular frequency. The result of this spread of color waves is a kaleidoscope or iridescent effect, similar to the colors we see in soap bubbles, CDs, and fish scales.